fix(dns): classify extended response codes

[ryanfowler]

Summary

• parse EDNS OPT extended RCODEs safely across DNS wire responses
• classify NXDOMAIN, NODATA, server errors, BADVERS, truncation, timeout, and malformed responses without string matching
• preserve family-error, fallback, retry, and authenticated-discovery behavior
• add table-driven wire and JSON status tests

Validation

• cargo fmt --check
• cargo clippy --locked --all-targets --all-features -- -D warnings
• cargo test --locked --all-features --lib --bins
• cargo test --locked --all-features --test cli --test formatting --test grpc --test har --test http --test install --test network --test terminal --test update --test websocket -- --test-threads=2